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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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package jdk.graal.compiler.truffle.hotspot;

import java.util.concurrent.atomic.AtomicReference;

import jdk.graal.compiler.serviceprovider.ServiceProvider;
import jdk.graal.compiler.truffle.host.TruffleHostEnvironment;

import com.oracle.truffle.compiler.TruffleCompilerRuntime;

import jdk.vm.ci.hotspot.HotSpotJVMCIRuntime;
import jdk.vm.ci.meta.ResolvedJavaType;

/**
 * This handles the Truffle host environment lookup on HotSpot without libgraal. For HotSpot without
 * libgraal the Truffle host runtime can be discovered using a static value, which was set on
 * registration.
 */
@ServiceProvider(TruffleHostEnvironment.Lookup.class)
public final class HotSpotTruffleHostEnvironmentLookup implements TruffleHostEnvironment.Lookup {

    private static final AtomicReference<TruffleCompilerRuntime> RUNTIME = new AtomicReference<>();
    private TruffleHostEnvironment environment;

    @Override
    public TruffleHostEnvironment lookup(ResolvedJavaType forType) {
        TruffleCompilerRuntime runtime = RUNTIME.get();
        if (runtime == null) {
            // fast-path non truffle
            return null;
        }
        TruffleHostEnvironment env = this.environment;
        if (env != null && env.runtime() == runtime) {
            // fast path truffle
            return env;
        }
        // in a HotSpot environment multiple compiler threads might lookup
        // the environment. Make sure we only create it once.
        synchronized (this) {
            env = this.environment;
            if (env != null && env.runtime() == runtime) {
                return env;
            }
            this.environment = env = new HotSpotTruffleHostEnvironment(runtime, HotSpotJVMCIRuntime.runtime().getHostJVMCIBackend().getMetaAccess());
        }

        return env;
    }

    public static boolean registerRuntime(TruffleCompilerRuntime runtime) {
        return RUNTIME.compareAndSet(null, runtime);
    }

}
